Spark plug



SPARK PLUG Filed Feb. ll, 1958 illlllIlllllllllllllllili.

, .lllllllllllllll -lllllllllill-lllllllllll lllllllllllllllllllllln \I- llilllllllllllllllllllllllll! Patented Aug. l', 1939 UNITED ISTATES PATENT OFFICE 2,168,26 t sramr PLUG Arthur c. Hastings, Jr., south Yarmouth, Mass.

Application February 11, 1933, SerlalNo. 190,057 9 cimas. (ci. 12s-169) This invention relates to a spark plug.

One object of the invention is to improve the construction cfa spark plug and more particularly of-a spark plug of the general type forming the subject matter of `my United States Letters Patent No. 2,069,951,` to increase the operating efficiency of the plug under varying conditions of service.

A further and more specific object of the in- 10 vention is to improve the construction of the firing end of a spark plug of the character described not only `with respect to its operating efciency under varying conditions of service but also to increase its durability and particularly to 'provide a spark plug having its ring' end constructed to resist, for long periods of time, corrosion and wear, resulting from the eifects of continual sparking during the use of the spark plug.

` A sun further object of theingenuon is to provide a novel and improved spark'plug and particularly a spark plug ofthe character referred to, whose construction is such as to facilitate the manufacture of the complete plug to the' end that liability of cracking of the insulating member of the plugmay be reduced to a minimum, while at the same time producing a construction of spark Yplug which is highly emcient inoperation, particularly under difficult service conditions such as are encounteredv in an oily engine.

With these objects in view and such others as may hereinafterappear, the `invention consists 'in the spark plug and in the various structures, arrangements and combinations of parts here- 435 inafter described and particularly defined in the claims 'at the end of this specification.

In the drawing, Fig. .1 is an elevation, partly in section of the preferred form of spark plug embodying the invention; Fig. 2 is an enlarged sec- 40 tional detail of the firing end of the spark plug shown in Fig. l; Fig. 3 is a similar view illustrat-` ing a modification of the spark plug shown in Fig.

l, and` Fig. 4 is a similar view illustrating still v another modification 'of the spark plug shown in Fig. 1. Y y

The different features of the present spark plug are preferably but not necessarily embodied in a spark plug of the general type forming the subject matter of my'United States Letters Patent No. 2,069,951, issuedy February 9, 1937 and as herein shown, the spark plug comprises an outer metallic sleeve III having a longitudinal bore I2 therethrough and a centrally disposed inner electrode I3 comprising a metallic rod or wire. The inner electrode may and preferably will comsion resisting alloy now upon `the market.

prise a corrosion `resisting element such as is now commonly used in spark plug manufacture and whichmay, for example, comprise a nickel-manganese alloy. The outer and inner electrodes Ill, I3 are preferably insulated by an insulating 5 member I4 of tubular form and preferably of thin refractory material and the tubular member I4 together with the inner electrode vI3 is arranged to project beyond the end of the metallic lsleeve III. The remaining elements of the spark l plug may and preferably will comprise those set forth in my Patent No. 2,069,951, above referred to, to which reference may be made.

Invaccordance with the present invention, the

ring end of the present spark plug is formed by 15 mounting a separate tip member 20 upon the end of the metallic sleeve 'I0 to form in eii'ect an extension thereof, and the tip member is preferably of tubular shape and arranged to surround the projecting portion of the insulating member- I4 201 to form the firing end of the plug. In thepreferred embodiment of the inventior the tip member 20 preferably comprises a corrosion resisting alloy such as a nickel-manganese alloy or it may vbe formed of other highnickel alloys including a 25 nickel chromium alloy or of any suitable corro- In the preferred form of the invention the tip member 29 of the outer electrode is formed of thin walls and of a size such as to very closely t the pro- 30 jecting en'd portion ofthe insulating member I4 to reduce to a minimum the liability of oil accumulation between the insulating member I4 and the.. tip member 20 of the spark plug. 'I'he tip member 2 0 may be'secured to the end portion 35 of the metallic sleeve III in various ways, as, for example, by being welded in the manner illustrated in Fig. 3, or thetip member may be provided with a flange and a portion`22 of a size such as to form a drivingv fit into the end of the bore 40 I2 of the sleeve I0.

It is preferred that the tip member 20 and the I projecting portions of the insulating member i4 and the inner electrode I3 may be related to one another so 'that the ends thereof lie in substan- 45 tially one plane to form the 4iiring end of the plug so that during operation the sparking occurs .across 'the end of the insulation from vone electrode to the other. f

In order tto increase the operating eiiiciency for 5I)l spark plugs of the general type illustrated in my patent above referred to, it hasbeen found that the reduced dimension -or thickness of the walls of the presentrtip contributes markedly to increasing the heat range within kwhich the present I6 body of the insulator l 4 at such a rate as to enable the end of the insulator I4 to remain in a Rmost efficient heated condition so as to enable the plug to operate under a relatively wide rangeof heat conditions in different engines while at the same time sufdcient heat is conducted away so as to prevent the firing end portion of the plug from getting hot enough .to cause detonation. Another explanation appears to be that the present construction of the firing end of the plug is such that the plug does not become excessively hot in the explosion part of thevcycle of operation ofthe engine but neither does it become excessively cool from the exhaust part of the cyclev of operation of theA engine, and as a result minimum fouling of the ring end of the plug has been found to occur even though the plug is used in hot and cool running engines and under oily conditions. v l

In order to resist the corrosive action due to Ithe continual sparking, I prefer to construct the tip of theplug of corrosion resisting alloys such as 95% nickel, 5% manganese, of nickel chromium alloys and in fact many suitable corrosion resisting alloys may be obtained upon the market. The thinness of the wall section of the present tip makes it desirable that/the tip be made of sucha corrosion resisting alloy in order that the plug may be operated for long periods of time.

In producing the present structure of plug I have experienced very satisfactory results using a center electrode' of 0.045 of an inch diameter.'

a porcelain insulating tube of from 0.025 to 0.026 of an inch wall thickness and with the metal tip 20 of the wall thickness of about 0.010 of an inch and ofan inside diameter of 0.103 of an inch. The metal tip is preferably arranged to fit around the projecting end of theinsulating tube I4 with minimum clearance and in practice a clearance of 0.001 of an inch has been found to provide a satisfactory joint.

Ihe present construction of spark plug may be utilized to facilitate the manufacture of the plug and the assembling of the insulating member with relation to the metal sleeve. It has been found desirable to construct a metal sleeve with a bore l2 of a size such as to provide substantial clearance between the walls of the bore and the insulating tube I4 such, for example, as a clearance of 0.005 of an inch so that the 'tube may be readily inserted into the bore with minimumliability of bending strains being placed upon the tube and hence minimum liability 'of cracking of the tube during the assembling ofthe component parts of the plug. By constructing the tip 2l so as to close- 1y t the end portion of -the insulating tube Il it has been found that this advantage may be secured while reducing oil accumulation to a minimum under varying conditions of use. Theinner electrode I3 may be cemented within the insulator I4 and the portion of the latter above the tip 20 cemented to the outer electrode Il.

In the modified form of spark plug shown in Fig. 3 the tip 2l may beprovided merely with the flange 24 and-the latter welded to the end of the outer electrode Il. In the modification illustrated l in Fig. 4 the thin tip member 20 constituting the firing end of the outer electrodemay be formed by depositing a thin lm or layer 30 of metal tice I may deposit this lm 30 by spraying or plating the same in accordance with the known `spraying and plating methods and the thin film 30 will be deposited to a sumcient thickness to comprise an extension of the sleeve l0 and to thereby produce a thin tubular metallic tip electrically connected with the sleeve I0 and firmly secured to the surface of the projecting portion of the insulator I4, all as is clearly illustrated in Fig. 4.

While the preferred embodiment of the invention has been herein illustrated and described, it will be understood that the invention'may be embodied in other forms within the scope of the following claims.

Having thus described the invention, what is claimed is: v

l. In a spark plug, an outer metallic threaded sleeve, an inner electrode, and a body of insulating material between the outer and inner electrodes, said inner electrode and insulating member projecting beyond the end of the threaded' sleeve, and a short preformed thin-walled metallic tubular member welded to the end of the sleeve and surrounding the projecting ends of the insulating member and inner electrode.

2. In a spark plug, an outer electrode provided with a bore, an inner electrode within said bore, a thin-walled elongated tubular insulating member disposed within and substantially filling the space between said outer and inner electrodes, the inner electrode and insulating member projecting beyond the end of the outer electrode, and a thin-walled tubular metal member mounted upon the end of the outer electrode and closely tting around said insulating member and being of a length commensurate with the projecting portions of the inner electrode and insulating member.

3. In a spark plug, an' outer metallic sleeve provided with a bore of substantially uniform4 'dimension throughout its length, an inner electrode within said bore and projecting beyond one and a separate thin metal tip member mounted on,

the end of the sleeve and surrounding the projecting portion of the insulating member so closely as to provide substantially no clearance whereby to control the operating temperature of said projecting portion of the insulating member.

:4. In a sp k plug, an outer metallic sleeve provided with a bore of substantially uniform dimension through its length, an inner electrode within said bore and projectingbeyond one end thereof, a thin walled elongated tubular insulating member of substantially uniform dimension through. I

out its length disposed within said bore between the metallic sleeve and the inner electrode, said insulating member being of a size suihciently smaller than the bore'to provide a clearance between' theinsulating Amember and the bore, a body of cement lling said clearance and a sepairate thin metal tip member welded to the end of the sleeve and surrounding the projectingpor;

tion of the insulating member so closely as to' provide substantially no clearance whereby to control the operating temperature of said projecting portion of the insulating member.'

5. In a spark plug, an` outer metallic sleeve provided with a bore of substantially uniform dimension throughout its length, an inner lelectrode within said borel a thin walled elongated tubular insulating member of substantially uniform dimension throughout its length disposed within and substantially iilling the space between said `outer metallic sleeve and said inner electrode, the inner electrode and insulating member 1 projecting beyond the end of said sleeve and a thin walled tubular metal member secured upon the end of the metallic sleeve to form a part thereof, the thinness of said tip controlling the operation temperature o'f the projecting portion of said insulating member.

6. In a sparkplug, an outer metallic sleeve provided with a bore of substantiallyuniform dimension throughout its length, an inner electrode` within said bore, a thin walled elongated tubular insulating member of substantially uniformv dimension throughout its length'disposed within and substantially iillirig the space between said outer metallic sleeve and said Iinner electrode, theinner electrode and .insulating member projecting beyond the end vof said sleeve and a thin walled tubular metal tip member mounted upon the end of said sleeve and closely iltting around the projecting portion of said insulating member whereby to control the temperature vof said projecting portion of said insulating member during use of the plug.

7. In a spark plug, an outer electrode comprising a sleeve having a bore, an inner electrode within said bore; a thin walled elongated tubular insulating member disposed within and substantially illling the space between said outer and said inner electrodes. said inner electrode and insulating member projecting beyond the end of mounted upon the end of said sleeve and closely tting around the projecting portion of said inisulating member whereby to control the'tempera-- ture of said projecting portion of said insulating member during' use of the plug. f

j 8. In a spark plug, an outer electrode comprising a sleeve havinga bore, an inner electrode within said bore, a thin walled elongated tubular insulating member disposed within and substan- Vtially lling the space between said outer and said inner electrodes, said inner electrode and insulatingmember projecting beyond the end of .said sleeve, and a tubular metal tip member of corrosion resisting lalloy welded upon the end of said sleeve and vclosely itting around the projecting portion of said insulating member whereby to control the operating temperature of said 4trode within said bore and projecting beyond one end thereof, a thin walled elongated tubular-insulating member'ofsubstantially uniform dimen' sion throughout its length disposed within said bore between the metallic sleeve and the inner electrode, said insulating lmember being of a size suiciently smaller than the boreto provide a clearance between the insulating member and the bore, a body ofv cement filling said clearance and a separate thin metal tip member welded upon the end ofthe sleeve and surrounding the projecting portion of the insulating member, said tip member being substantially the length oi' said projecting portion of the insulating member.

M ARTHURC. HABTINGS, Jn..

.said sleeve and a tubular metal tip member 

